INTRODUCTORY OBSERVATIONS. 19 
Order II. vropeEta. 
Body long, slender. Feet always four. Tail long, per- 
sistent. Ribs very short. Vertebra numerous and move- 
able. Respiration at first aquatic by external branchiz, 
which are never concealed within the chest; afterwards 
atmospheric by cellular lungs. Tympanum concealed. 
Impregnation effected by sexual contact, at least in most 
instances 
Genera. Salamandrina, Salamandra, Molge. 
Order III. Aampuipneusta. 
Body elongate, formed for swimming. Feet either four 
or two anterior only. Tail compressed, persistent. Re- 
spiration aquatic by means of branchize throughout life, 
co-existing with rudimentary lungs. Branchize external, 
persistent. Eyes with palpebre. 
Genera. Proteus, Siren, Menobranchus, &c. 
Order IV. aprancuta. 
Body long, formed for swimming. Feet four. Cranium 
sclid. Tail compressed. Respiration by means of lungs 
‘ouly. “Branchiz none. No metamorphosis known. 
Genera. Menopoma, Amphiuma, &ce. 
Order V. avopa. 
Body elongate, slender, anguiform. Feet none. Tail 
very short, almost wanting. Lungs one larger than the 
other. (The existence of branchie at any period of life 
